云南龙陵勐糯铅锌矿床中镉元素赋存状况     

赵发  赵喷 《云南地质》2010,29(1):49-52

矿床中镉元素异常明显,以硫镉矿、不规则粒状、脉状充填嵌布于闪锌矿中。提出矿石生成顺序,为进一步找矿提供新依据。  相似文献   

A 3000-year varved record of glacier activity and climate change from the proglacial lake Hvítárvatn,Iceland     

Darren J. Larsen  Gifford H. Miller  Áslaug Geirsdóttir  Thorvaldur Thordarson 《Quaternary Science Reviews》2011,30(19-20):2715-2731

A suite of environmental proxies in annually laminated sediments from Hvítárvatn, a proglacial lake in the central highlands of Iceland, are used to reconstruct regional climate variability and glacial activity for the past 3000 years. Sedimentological analysis is supported by tephrostratigraphy to confirm the continuous, annual nature of the laminae, and a master varve chronology places proxies from multiple lake cores in a secure geochronology. Varve thickness is controlled by the rate of glacial erosion and efficiency of subglacial discharge from the adjacent Langjökull ice cap. The continuous presence of glacially derived clastic varves in the sediment fill confirms that the ice cap has occupied the lake catchment for the duration of the record. Varve thickness, varve thickness variance, ice-rafted debris, total organic carbon (mass flux and bulk concentration), and C:N of sedimentary organic matter, reveal a dynamic late Holocene climate with abrupt and large-scale changes in ice-cap size and landscape stability. A first-order trend toward cooler summers and ice-cap expansion is punctuated by notable periods of rapid ice cap growth and/or landscape instability at ca 1000 BC, 600 BC, 550 AD and 1250 AD. The largest perturbation began ca 1250 AD, signaling the onset of the Little Ice Age and the termination of three centuries of relative warmth during Medieval times. Consistent deposition of ice-rafted debris in Hvítárvatn is restricted to the last 250 years, demonstrating that Langjökull only advanced into Hvítárvatn during the coldest centuries of the Little Ice Age, beginning in the mid eighteenth century. This advance represents the glacial maximum for at least the last 3 ka, and likely since regional deglaciation 10 ka. The multi-centennial response of biological proxies to the Hekla 3 tephra deposition illustrates the significant impact of large explosive eruptions on local environments, and catchment sensitivity to perturbations.  相似文献   

Heat of formation of petalite, LiAlSi4O10     

D. W. Faßhauer  L. Cemič 《Physics and Chemistry of Minerals》2001,28(8):531-533

The enthalpy of formation of petalite, LiAlSi₄O₁₀, has been measured using high-temperature solution calorimetry. The measurements were carried out in a Calvet-type twin micro calorimeter at 728?°C. A 2PbO?·?B₂O₃ melt was used as a solvent. Tabulated heats of formation of the components and tabulated heat capacities of the reactants and the product (Robie and Hemingway 1995) were used to calculate the standard heat of formation of petalite from the measured heats of solution. The calculations yielded a mean value of Δ _f H ^pet _298.15=?4872±5.4 kJ mol^?1. This value may be compared to the heat of formation of Δ _f H ^pet _298.15= ?4886.5±6.3 kJ mol^?1 determined by the HF solution calorimetry by Bennington et?al. (1980). Faßhauer et?al. (1998) combined thermodynamic data with phase-equilibrium results to obtain best-fit thermodynamic results using the Bayes method, in order to derive an internally consistent dataset for phases in the NaAlSiO₄– LiAlSiO₄–Al₂O₃–SiO₂–H₂O system. They determined ?4865.6?±?0.8?kJ?mol^?1 as the enthalpy of formation of petalite, a value that is appreciably closer to the enthalpy found in this work.  相似文献   

距今五千年左右环境恶化事件对我国新石器文化的影响及其原因的初步探讨   总被引：21，自引：0，他引：21  

朱艳  陈发虎  张家武  安成邦 《地理科学进展》2001,20(2):111-121

距今五千年左右全球普遍存在一次变化幅度较大的突发性环境恶化事件 ,此事件导致各地生态环境发生了较大的变化 ,与此同时的我国新石器文化表现为衰退和在某些地点的中断。气候环境变化是该时段影响人类文化发展变化的主要因素。环境变化对史前文化影响的可能原因是 :气候变化导致生态环境变化 ,生态环境变化导致直接影响人类生存的生物营养源的变化 ,进而导致史前文化的变化。  相似文献   

大厂锡矿床硅,氧同位素地球化学   总被引：8，自引：1，他引：8  

韩发  沈建忠 《矿物学报》1994,14(2):172-180

本文对大厂锡矿床不同类型石英和岩石进行系统的硅、氧同位素研究表明，各类矿化体中石英的硅同位素组成几乎相同，而且它们又与直接容矿硅质岩的δ30Si值十分接近，但完全不同于矿区侵入岩的有关值。这说明层状矿体中的石英与直接窑矿硅质岩有相同的硅质来源，后期各类脉状矿化过程中的硅质来自容矿硅质岩，而不是花岗岩。层状矿体中荣带状岩石和含冰长石混合样的δ30Si值为-0．3‰±0．2‰，这组负值可能是由冰长石引起的。但冰长石中的硅是由海底热水活动系统还是火山灰尘提供尚待研究。对比发现，本矿区硅质岩δ30Si值与部分深海（洋壳区）、半深海（陆壳区）放射虫硅质岩有关资料相似，但其δ18O值低于全球各类硅质岩，它们可能是在海底热水活动与生物化学作用共同参与下形成的。  相似文献   

Ohne Fallgewicht arbeitender Fernauslöser     

Prof. H. Ambühl  Das Gerät ist erhältlich bei Fa. Dr. H. Züllig 《Aquatic Sciences - Research Across Boundaries》1983,45(2):502-504

A device is described which can be used where working equipment has to be instantly activated (i.e. without time delay) under water. The latch with an adjustable spring, on which the instrument is fastened, can be released by jerking on the supporting cable or by suddenly stopping the lowering motion, thereby instantly activating the working equipment.   相似文献   

吐哈盆地西南缘古流体地质作用与砂岩型铀矿成矿作用初探   总被引：9，自引：0，他引：9  

吴伯林  黄志章  李秀珍  张发 《铀矿地质》2003,19(6):326-332

笔通过岩石后生蚀变与气-液包裹体特征研究,认为吐哈盆地西南缘中-下侏罗统水西沟群(J1—2sh)地层存在两期明显的古流体地质作用：早期酸性氧化古流体和晚期碱性还原古流体地质作用。前造成本区J1—2Sh地层由“黄色”及“红色”蚀变岩石组成的层间氧化带的广泛发育,该期古流体作用对铀成矿极其有利;后是本区“钙质层”形成的主要原因,对铀成矿不利。据气-液包裹体成分测试结果初步认为：古流体的组成主要是地下水及煤成天然气。  相似文献   

The Upper Valanginian (Early Cretaceous) positive carbon-isotope event recorded in terrestrial plants     

Darren R. Gröcke  Gregory D. Price 《Earth and Planetary Science Letters》2005,240(2):495-509

Our understanding of the ancient ocean-atmosphere system has focused on oceanic proxies. However, the study of terrestrial proxies is equally necessary to constrain our understanding of ancient climates and linkages between the terrestrial and oceanic carbon reservoirs. We have analyzed carbon-isotope ratios from fossil plant material through the Valanginian and Lower Hauterivian from a shallow-marine, ammonite-constrained succession in the Crimean Peninsula of the southern Ukraine in order to determine if the Upper Valanginian positive carbon-isotope excursion is expressed in the atmosphere. δ¹³C_plant values fluctuate around − 23‰ to − 22‰ for the Valanginian-Hauterivian, except during the Upper Valanginian where δ¹³C_plant values record a positive excursion to ∼− 18‰. Based upon ammonite biostratigraphy from Crimea, and in conjunction with a composite Tethyan marine δ¹³C_carb curve, several conclusions can be drawn: (1) the δ¹³C_plant record indicates that the atmospheric carbon reservoir was affected; (2) the defined ammonite correlations between Europe and Crimea are synchronous; and (3) a change in photosynthetic carbon-isotope fractionation, caused by a decrease in atmospheric pCO₂, occurred during the Upper Valanginian positive δ¹³C excursion. Our new data, combined with other paleoenvironmental and paleoclimatic information, indicate that the Upper Valanginian was a cool period (icehouse) and highlights that the Cretaceous period was interrupted by periods of cooling and was not an equable climate as previously thought.  相似文献   

吉林省中部早石炭世杜内期的腕足动物化石   总被引：1，自引：0，他引：1  

刘发 《吉林大学学报(地球科学版)》1988,(4)

描述的化石是采自吉林省中部杜内期北通气沟组,共17个属24个种,包括3个新种。这个动物群的特点与我国南方杜内期动物群的特点不同,而与美国密西西比系金德胡克组、苏联库茨纳兹盆地和莫斯科盆地杜内期的动物群非常相像。类似的动物群在新疆、甘肃和内蒙等省和自治区均已发现。吉中地区杜内期腕足动物群,属于北美—西伯利亚古生物地理区系。  相似文献   

辽宁本溪地区本溪组下部腕足类化石的发现及其意义   总被引：4，自引：0，他引：4  

刘发 《吉林大学学报(地球科学版)》1987,(2)

本文描述了辽宁本溪地区中石炭统下部的腕足类化石共12个属18个种,其中新种6个。并对它的时代进行了讨论,提出了本溪统下部层位的腕足动物化石具有早石炭世晚期到中石炭世早期的色彩,并将本溪地区本溪统下部紫红色岩段划出,建立一个新组一田师付组。并且认为田师付组可与甘肃靖远组对比与苏联的巴什基尔组相当。  相似文献